1. Field of the Invention
The present invention relates to a linear motion guide unit having wide application in sliding parts incorporated in a variety of machines and apparatus including, for example, semiconductor manufacturing equipments, precision measurement/inspection instruments, precision-assembling machines, and so on. More particularly, it relates to a linear motion guide unit in which a slider is allowed to move relatively to an elongated track rail by virtue of rolling elements.
2. Description of the Prior Art
Although the linear motion guide units have come to be used extensively in machinery in fields as diverse as semiconductor manufacturing equipments, measurement/inspection instruments and so on, the expansion of their uses accompanied by the current developments in advanced technologies requires more and more such linear motion guide units that can manage growing demands for less noise, low-frictional resistance, long-lasting service life, high precision, high-speed sliding motion, easy assemblage, versatility and the like. With the prior linear motion guide units, moreover, the slider is commonly provided with a lower seal to keep the foreign matter such as dirt and dust against entering inside a raceway or a raceway groove, resulting in ruin of the sliding performance of the slider relatively to the track rail, and also prevent the contaminants including debris, metal cuttings and so on, which might occur in the linear motion rolling guide unit in itself, from escape outside the linear motion guide units.
In Japanese Patent No. 3237981, which was granted for a senior invention of the same applicant as in the present application, there is disclosed a linear motion guide unit in which the slider is mounted with the lower seal. With the prior linear motion guide unit, the lower seal is designed to make attachment to and/or detachment from the slider much easier and envisaged to make sure of a room ample in height above the top of the base on which the track rail lies and underneath the slider that fits astride over the track rail. The slider is composed of a carriage, and end caps attached on forward and aft ends of the carriage, one to each end. The end cap has a lug underneath, which extends downward along the side closer to the track rail and terminates in hooks. The lower seal is made up of a metal backing plate and an elastic member, both of which are made therein with holes to fit the lug therein, which are located in such relation to one another that an edge of the hole in the elastic member is partially inside the hole made in the metal backing plate. To fasten the lower seal to the end cap, the lug on the end cap is first forced to fit into the lower seal while having the hole edge of the elastic member deformed elastically, and then the hook comes into biting engagement with the hole edge of the metal backing plate to accommodate the lower seal within a room reserved for any grinding tool in the carriage of the slider.
With the linear motion guide unit constructed as recited just above, nevertheless, the first and second holes located in offset relation to one another in the lower seal would need urging the lug of the end cap into the holes while having the elastic member of the lower seal deformed elastically to assemble the lower seal with the slider. Thus, this prior construction has to go through some chores of pressing the lower seal to the end cap against elasticity of the elastic member in the lower seal. Moreover, the hooks on the lug of the end cap, because of made in a way extending towards the front or the rear, should not be able to extend as long as desired to make sure of certain biting engagement of the hooks with the lower seal. Thus, the biting engagement of the hooks with the lower seal in the prior slider recited earlier is too small in size to make ensure the satisfying engagement of the hooks with the lower seal safely.
The present invention, therefore, has as its primary object to overcome the problem as described just above and more particular to provide an improved linear motion guide unit in which a secure fastening of a lower seal to an end cap of a slider can be indeed ensured with just a slight lengthwise shift of the lower seal relatively to the associated end cap after a lug of the end cap has fit in a recess made in the lower seal.
The present invention is concerned with a linear motion guide unit; comprising a track rail made on a lengthwise side thereof with a first raceway surface, a slider movable lengthwise along the track rail, the slider having a second raceway surface in opposition to the first raceway surface, a rolling element running through a load raceway defined between the confronting first and second raceway surfaces, and a lower seal installed underneath the slider to close the load raceway; wherein the slider is provided on a bottom surface thereof with a lug terminating in a hook that juts widthwise and extends lengthwise of the slider; wherein the lower seal is made therein with a first hole allowing the lug to fit therein, and a second hole connected to the first hole in longitudinal direction of the lower seal and made on at least any one lengthwise edge thereof with a tooth that will come into hooked engagement with the hook on the lug; and wherein the lug of the slider fits in the first hole in the lower seal and then is moved into the second hole relative to the lower seal to fasten the lower seal to the slider. With the linear motion guide unit of the present invention stated earlier, it is to be under stood that the rolling element may be either a ball or a roller, and the terminology xe2x80x9craceway surfacexe2x80x9d includes xe2x80x9craceway groovexe2x80x9d. Moreover, the words xe2x80x9cat least one lengthwise edgexe2x80x9d is the conception applied, not only to any one side, to both sides.
In one aspect of the present invention, a linear motion guide unit is provided in which the slider is comprised of a carriage made with the second raceway surface and a return passage allowing the rolling element to run through there, end caps fastened to lengthwise opposite ends of the carriage, one to each end, and made therein a turnaround to connect the second raceway surface to the return passage, getting the rolling element turning about there in running direction thereof and further made thereon with the lug, the end seal fastened to the end caps, and a retainer extending along by the carriage to keep the rolling element in place. It is to be understood that the terminology xe2x80x9cretainerxe2x80x9d used earlier has the conception including all the shape like rod, plate or band.
In another aspect of the present invention, a linear motion guide unit is provided in which both the first and second holes formed in the lower seal are made at lengthwise opposite ends of the lower seal so as to parallel the lugs of the end caps in a way oriented in the same direction along the longitudinal direction and also arranged at the same interval with one another. In a further another aspect of the present invention, there is disclosed a linear motion guide unit in which the lug made on the slider to fasten the lower seal thereto is located at a flat bottom area near the track rail over a space reserved underneath the end cap.
In another aspect of the present invention, a linear motion guide unit is provided in which a lengthwise dimension of the lug on the slider is made almost the same size in length as each of the first and second holes in the lower seal.
In another aspect of the present invention, a linear motion guide unit constructed is provided in which the lower seal includes a backing plate having a tooth extending lengthwise along at least one edge of the second hole, and an elastic sealing member adhering to the backing plate to close the load raceway. In another aspect of the present invention, there is disclosed a linear motion guide unit in which the backing plate of the lower seal is composed of a major flat portion where there are formed both a slot edged with the tooth to define the second hole and a window connected lengthwise with the slot to define the first hole, and a slanting portion integral with the major flat portion and extending lengthwise while making face-to-face engagement with a slantwise surface area that extends over the space left open just underneath the slider. In a further another aspect of the present invention, there is disclosed a linear motion guide unit in which the tooth made on the backing plate of the lower seal has at a sidewise edge thereof a sealing tip that will come into engagement with a pedestal of the lug on the slider.
In another aspect of the present invention, a linear motion guide unit is provided in which the sealing member of the lower seal includes a first sealing part adhering to a lower side of the backing plate and extending over an entire length of the backing plate, a second sealing part lying lengthwise on an upper side of the backing plate in a fashion bulging out up to coming into contact with a slantwise surface area over the space where a lengthwise bottom surface of the carriage is partially cut away, and a third sealing part lying on the upper side of the backing plate along a longitudinal bottom surface of the end cap. In a further another aspect of the present invention, there is disclosed a linear motion guide unit in which the first sealing part is made therein with an opening to define the second hole and a pocket constituted with the first hole that is connected lengthwise with the opening and closed with a thin bottom, and wherein the opening is larger in widthwise dimension than the slot edges with at least one tooth formed on the backing plate and roughly equal in width with the hook, while the pocket is substantially equal in width with the window in the backing plate.
In another aspect of the present invention, a linear motion guide unit is provided in which the thin bottom is made with a traverse ridge raised above the thin bottom towards the backing plate along a traverse edge of the thin bottom. After the lower seal has been fastened to the end cap, the thin bottom in the lower seal comes into engagement at the traverse ridge thereof with any adjacent one of the forward and aft ends of the hook of the lug to close the second hole in the first sealing part, helping improve the sealing performance of the lower seal.
In another aspect of the present invention, a linear motion guide unit is provided in which the first sealing part involves a first lip extending in the longitudinal direction of the lower seal so as to come into engagement with any associated side of the track rail, and a second lip made to extend lengthwise to make sliding engagement with the slantwise surface area beneath which the space is left open.
In another aspect of the present invention, a linear motion guide unit is provided in which a pedestal of the lug jutting out of the end cap of the slider is made with a recess extending lengthwise between the hook and a bottom surface of the end cap, so that the lower seal is fastened to the end cap after the tooth made on the backing plate of the lower seal has come into engagement with the recess. With the linear motion guide unit constructed as stated earlier, the lug made on the slider first fits in the pocket below the backing plate of the lower seal, and then the recess on the lug fits over the tooth on the lower seal to fasten the lower seal to the end cap.
In a further aspect of the present invention, a linear motion guide unit is provided in which the slider fits over the track rail for linear movement relative to the track rail.
According to the linear motion guide unit of the present invention constructed as recited earlier, while the end cap of the slider is made on the bottom surface thereof with the lug terminating in the hooks, the lower seal has both the first hole allowing the lug to fit therein and a second hole edged lengthwise with the teeth that may make engagement with the hooks. Thus, certain engagement of the hooks on the lug of the end cap with the teeth of the lower seal to make sure of fastening securely the lower seal to the slider can be easily accomplished by just the act of first introducing the hooks into the first hole in the lower seal and then slightly moving the hooks into the second hole where the hooks come in hooked engagement with the teeth of the lower seal.
With the linear motion guide unit constructed as stated earlier, the lower seal can be mounted easily, securely to the end cap with the sealing member in the lower seal being less subject to elastic deformation when fastened to the end cap. Moreover, the fastening construction of the present invention makes it possible to certainly, smoothly and securely install the lower seal in the slider without causing any damage that might take away any of the sealing effects even for the large linear motion guide units.